A series of K1–2x–2y Ba y Al11O17(KBAO):xEu2+ phosphors are designed to develop a blue phosphor with excellent thermal properties. All of the samples present similar β-Al2O3 structures with P63/mmc space group; the K+ vacancy can exist stably until the Ba2+ concentration exceeds around y = 0.3. KBAO:Eu2+ exhibits strong absorption for near-ultraviolet light and relatively standard blue emission. The mechanisms for excitation and emission spectrum variations have also been studied in detail. Based on the adjustment of K+ vacancy numbers in the defect structure, K0.6Ba0.1Eu0.1Al11O17 exhibits a remarkable quantum yield of around 91.2% and a terrific high-temperature characteristic. The zero-thermal quenching performance mainly results from stabilization of the flowing electron number between Eu2+ 5d levels and K+ defect ε­(0/–1) and ε­(+1/0) levels in the processes of thermal ionization and recombination. A bright fabricated white-light-emitting diode (WLED) gives a color rendering index (CRI) of R a = 87 and a correlated color temperature (CCT) of 4510 K, demonstrating that KBAO:Eu2+ has application potential to provide a blue light component in WLED. In addition, our research is a significant attempt to achieving stable zero-thermal quenching by subjective structure design, which provides a reference value for investigating the excellent new phosphors.

Nowadays liquid crystal displays (LCD) backlighting has become an independent subject of the display field, and gradually formed a research and development hotspot. The narrow-band emitting phosphors which play an...

The excellent narrow-band emitters, especially the green ones, are regarded as a pivotal research direction for light-emitting diodes (LED) backlights in liquidcrystal displays (LCDs). A nearly single-peak green emission centered at 513 nm with a full width at half maximum of 28 nm is reached in KAl 11 O 17 :0.1Eu 2+ , 0.15Mn 2+ phosphor via nearly 100% energy transfer (ET) efficiency, and the extended X-ray absorption fine structure analysis elucidates its mechanism, which is that Eu 2+ and Mn 2+ are constrained to form Eu 2+ -Mn 2+ pairs with a small distance 3.7 Å caused by the local environment relaxation inducement. Meanwhile, by creating an unhindered energy flow between Eu 2+ , Mn 2+ and K + /O 2− defect levels through ET and multilevel electron trapped and recombination process, the KAO:Eu 2+ , Mn 2+ phosphors perform superb photoluminescence property with a high color purity of 83%, an excellent thermal stability (94%@200 • C), and unexceptionable internal and external quantum efficiencies of 91.7% and 66.4%, which all are superior to characteristics of commercial β-SiAlON:Eu 2+ phosphor. Moreover, the white LED fabricated using KAO:Eu 2+ , Mn 2+ to provide green component shows a wide color gamut of 105% National Television System Committee. These results indicate a potential for an application of our material in LCD-LED backlights, and the design of such local relaxation-induced structure provides a significative reference to develop the new narrow-band emitters.

A series of Na0.5Bi2.5Nb2−xTaxO9 (NBN2−xTx):Er3+/Yb3+ upconversion luminescence (UL) phosphors were prepared by a solid‐state sintering method, and the lattice structure of the prepared samples was studied by X‐ray diffraction. Under 980‐nm laser excitation, the UL properties were investigated by a spectrophotometer from room temperature to 723 K, and the optimal concentration of co‐doping Er3+/Yb3+ is 0.14 and 0.26 by replacing Bi3+ sites in NBN2−xTx host, respectively. With the increase of Ta5+ concentration, the color of UL gradually changes from green to yellow corresponding color coordinates from (0.301, 0.682) to (0.441, 0.549) under 980‐nm laser excitation. This color change is attributed to the decrease of lattice unit volume leading to the increase of cross relaxation of Er3+ to Er3+ and energy back transfer from Er3+ to Yb3+. Using the luminescence intensity ratio technique, the maximum absolute sensitivities (SA) are obtained as 0.00674 K−1 at 538 K and 0.00603 K−1 at 573 K, and relative sensitivities (SR) are obtained as 0.01174 K−1 at 303 K and 0.01244 K−1 at 303 K based on 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 energy level transitions of Er3+ in NBN2:0.14Er3+/0.26Yb3+ phosphors under 980‐ and 1550‐nm laser excitations, respectively. The results suggest that the NBN2−xTx:Er3+/Yb3+ phosphors are promising candidates for temperature sensing with different UL colors.

White light-emitting diodes (WLEDs) are always fabricated by a combination of the near-ultraviolet (n-UV)-emitting LED chip with tricolor emitting phosphors.However, improving the color rendering index (CRI) is limited due to the absence of cyan composition for common commercial combinations. Based on this, a series of blue-cyan dual-peaks emission Ca 4−x Lu 2x Hf 1−x Ge 3 O 12 (CLHGO):Bi 3+ phosphors with unique adjustability are developed by the solid solution design strategy. All the samples belong to the garnet structure with the Ia3d space group. Two relatively independent segregation structures [Ca 4 HfGe 3 O 12 ] and [Ca 3 Lu 2 Ge 3 O 12 ] are established in the samples. When Bi 3+ ions enter into the highly symmetrical hexagon coordination environment, a special phenomenon appears that the emission peaks consist of two stabilized narrowband emission bands at 435 and 475 nm, their intensity ratio could change continuously with the increase of solid solubility. All these results are confirmed by means of excitation and emission spectra, first principles calculation and decay curves. The Ca 3.4 Lu 1.2 Hf 0.4 Ge 3 O 12 :Bi 3+ sample, with a high efficiency around 84.1% and an excellent thermal stability (65.6%@150 • C), is chosen as the optimal sample to improve the blue and cyan compositions for full spectrum emission. Using the Ca 3.4 Lu 1.2 Hf 0.4 Ge 3 O 12 :Bi 3+ , commercial green (Ba, Sr) 2 SiO 4 :Eu 2+ phosphor, and commercial red CaAlSiN 3 :Eu 2+ phosphor on a 360-nm n-UV LED chip to fabricate WLED, which successfully bridge the cyan gap and the CRI value of the as-fabricated warm-white LED reaches 90.2. The previous results confirmed that CLHGO:Bi 3+ phosphors have promising application prospect in the development of n-UV-pumped warm-white LEDs with high-CRI values. The unique property performance originating from independent segregation structures provides more reference for the research on photoluminescence mechanism.